Fuselage

ABSTRACT

The fuselage according to an exemplary embodiment is conceived in such a way as to prevent the spread of flames produced by a source of fire and acting on the fuselage from outside the aircraft environment. The fuselage concept takes into account materials or material combinations that will scarcely allow protection of the cabin area of an aircraft (upon emergency landing) to be violated by flames spreading from outside the aircraft environment, which may facilitate an evacuation of passengers from the aircraft. An aircraft fuselage, whose fuselage structure, in addition to other structural elements that are components of the mechanical strength bracing of the fuselage and help absorb its forces, encompasses an exterior skin consisting of various respective materials, which are designed to be resistant to shear, and incorporated as a bearing element into the mechanical strength bracing to absorb and transfer the forces and torques acting thereupon. The exterior skin is fabricated from a burn-through resistant semi-finished material consisting of a non-metallic material or a fireproof metallic material, wherein the semi-finished material can be molded through further processing. Also, the exterior skin may be realized by a semi-finished material combining a non-metallic material and a metallic material, wherein the produced exterior skin product is a hybrid material that can be molded and joined through further processing.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority of DE 10 2004 001 078 filed Jan.05, 2004 and U.S. Ser. No. 60/600,105 filed Aug. 09, 2004, which areboth hereby incorporated by reference.

FIELD OF THE INVENTION

The invention relates to a fuselage in particular of a commercialaircraft.

BACKGROUND OF THE INVENTION

In the past, aluminium structures were highly successful in aircraftconstruction. Without going any further into detail on this matter, anyexpert, and most likely even a layman enthusiast interested in aircraftconstruction, knows that the traditional structural design of a fuselageinvolves an outer fuselage skin made solely of aluminium or aluminiumalloys. Prior art provides the relevant examples for this.

There are accidents that were regrettably traced back to fires caused bykerosene leaking from an aircraft that had performed an emergencylanding. Due to this, there may be a need for an aircraft having animproved fire protection.

In the event of a fire started during an emergency belly landing of anaircraft, (ignited) burning kerosene leaking from the aircraft may causeboth the aluminium airframe of the aircraft structure and the interiorinsulation to burn through or away.

Publication “WO 00/75012 A1” now discloses a solution with which anyoutbreak of fire can be countered in the emergency situation described.This solution relates to fuselage insulation for one aircraft fuselagereferred to as “fire-resistant”. This publication discloses aninsulating package lying inside an expanse between the interior fuselagecladding and exterior fuselage skin as a primary insulation. Areas ofthis insulation package are here protected by a film consisting offire-resistant material (“fire blocking material”), wherein thisfire-resistant film area directly faces the exterior skin of theaircraft fuselage (like a fire protection shield). In addition to thefact that this proposal can only provide inadequate protection of theinsulation package and the interior fuselage area against fires, sincegiven a catastrophic fire, the flames from the fire that pass preciselyfrom outside the aircraft through a damaged exterior skin and approachthe interior insulation a short time later, i.e., also pass through the(only) fire-resistant, but not fireproof film given prolonged exposureto fire, the intended area-by-area arrangement of a merelyfire-resistant film would be unable to ensure a sufficient level of firesafety relative to the interior fuselage area. The publication alsoproposes corresponding attachment elements for securing the fuselageinsulation, which most often consist of plastic(s), e.g., a polyamide.

The publication makes no mention of additional measures available forpreventative fire protection, which are geared toward the technicaldesign of the aircraft fuselage in terms of fire safety, andadditionally aimed at the external fuselage skin.

SUMMARY OF THE INVENTION

According to an exemplary embodiment of the present invention, anaircraft fuselage may be provided, comprising an exterior skin product.The external skin product is made of a semi-finished material. Thesemi-finished material is a combination of a non-metallic material and ametallic material. The exterior skin product is a hybrid material thatis moldable and joinable through further processing.

According to another exemplary embodiment of the present invention, anaircraft fuselage may be provided, comprising an exterior skin which isfabricated from a burn-through resistant semi-finished material made ofa non-metallic material or a fireproof metallic material, wherein thesemi-finished material can be molded through further processing.

The fuselage according to an exemplary embodiment of the presentinvention may be is conceived in such a way as to prevent the spread offlames produced by a source of fire and acting on the fuselage fromoutside the aircraft environment. The fuselage concept takes intoaccount materials or material combinations that will scarcely allowprotection of the cabin area of an aircraft (upon emergency landing) tobe violated by flames spreading from outside the aircraft environment,which is believed to tangibly facilitate an evacuation of passengersfrom the aircraft. Furthermore, it is believed that the fire safety ofan outside or external fuselage skin of an aircraft fuselage may beimproved in such a way as to achieve a high burn-through behavior of theskin.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in greater detail with reference to anexemplary embodiment with reference to the following drawings.

FIG. 1 shows an aircraft fuselage of a passenger aircraft depictingelements of the fuselage structure and interior equipment according toan exemplary embodiment of the present invention;

FIG. 2 shows a selected area of the external skin and other structuralelements of the fuselage structure according to an exemplary embodimentof the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 shows an excerpt of a cross section of the fuselage from apassenger plane, restricted to a sectional area of an aircraft passengercabin 1. This arrangement would likely be familiar an expert in aircraftconstruction, and discloses relations from which the observer mayrecognize that a combustible interior cladding 3 is situated very close(in terms of the fuselage) to the external skin 2, which when installedtogether with the exterior skin 33 encompasses a space 19 within whichthe fuselage insulation (not shown on FIG. 1) is installed. If anexterior skin 2 traditionally realized with an aluminum material oraluminum alloy is installed in this configuration, the observer will beable to weigh the extent of a catastrophic fire of the kind described atthe outset. The additional parts and elements of the interior equipmentand fuselage structure shown on FIG. 1 and integrated into an aircraftpassenger cabin 21 (based on the example therein) will not be described,since they are considered to be irrelevant with respect to the presentinvention.

FIG. 2 shows a skin field section of the exterior skin 2 that is affixedto the stringer 8. The skin field is restricted to the area of skinbordered by two ribs 6, 7 secured to the stringer, which are alignedperpendicular to the fuselage longitudinal axis. For the sake ofcompleteness, let it be mentioned that the exterior skin 2, thestringer(s) 8 and the ribs 6, 7 are constituents of the mechanicalstrength bracing of the fuselage, and participate in its absorption offorces, wherein the exterior skin 2 consists of different respectivematerials, generally of the mentioned material “aluminum or aluminumalloy”, which are designed to be resistant to shear. The exterior skin 2is incorporated into the mechanical strength bracing as a bearingelement to absorb and transfer the forces and torques acting thereupon.

It is believed that the proposed solution follows the concept of aprophylactic or preventative fire safety for an aircraft, so that aninduced high burn-through behavior of the exterior skin 2 may increasethe technical fire safety of a passenger or military aircraft, first andforemost of a passenger plane, so that it is believed that a firesituation of the kind described at the outset cannot develop into acatastrophe, e.g., after an aircraft has made a successful emergencylanding.

The proposed solution is based A) on the use of a material for exteriorskin 2, which is provided with a fireproof (plate-like) semi-finishedmaterial consisting of a non-metallic material or a fireproof metallicmaterial, wherein the semi-finished material can be molded throughfurther processing to convert the inwardly curved contour of thefuselage skin 2.

On the other hand, B) proposes that the exterior skin 2 be realized bycombining a semi-finished material comprised of a non-metallic materialand a metal material. The produced exterior skin product of such amaterial combination is a hybrid material, which can be molded andjoined through further processing. This material combination is achievedby means of a non-metallic material consisting of carbon and glassfibers (in mixed-fiber architecture) or only carbon and glass fibersand/or ceramic fibers, and a metal material, wherein the metal materialconsists of an aluminum or a titanium or an aluminum or titanium alloy.

The desired arrangement is coated by a resin layer or imbedded in aresin. The obtained exterior skin product with this material combinationhas a sandwich design. This sandwich design is adhesively bonded with acomposite material and the mentioned metal material in layers (films),which yields a burn-through resistant behavior of the exterior skinrelative to long-term exposure to flames from a fire. In addition, thesandwich design can be realized using a glare material, whoseburn-through behavior is high.

Returning to these steps A) and B), we expand the scope by manufacturingthe exterior skin 2 [or processing the semi-finished material] using anon-metallic material consisting of a carbon fiber material or a glassfiber material or a ceramic fiber material or a silicate fiber material.One would also have to remember that a material combination comprised ofthe various non-metallic materials is taken into account whenmanufacturing the exterior skin (2) according to B). In this case, it isprovided that the non-metallic material be realized with plasticsreinforced with glass or plastic fibers (a GFK and/or CFK material). Thementioned material combination can here be realized with a GFK or CFKmaterial and aluminum or titanium or alloys thereof.

The mentioned composite material involves a heatproof compositematerial, whose behavior also exhibits a temperature resistance andtensile strength. It is proposed that this heatproof material berealized with carbon fibers, coated with material from a nitride orcarbide bond, e.g., silicon carbide, silicon nitride or boron nitride,and a metal or ceramic material, into which the coated carbon fibers areimbedded.

Further, the fireproof, metallic material mentioned relative to A) isrealized with titanium or a titanium alloy.

In order to complement the concept of preventative fire safety (examinedhere) for an aircraft, C) additionally proposes that the outer surfaceof the (burn-through resistant) exterior skin 2, namely the area of skinexposed to weathering from the outside environment of an aircraft, bejoined with a plate-like planking 5 based on the example on FIG. 2. Thisplanking 5 is also to be realized with the burn-through resistantsemi-finished product using a non-metallic material or a fireproofmetallic material. On the other hand, it is possible to realize theplanking 5 according to B) with the mentioned material combination ofthe semi-finished product using a non-metallic material and a metalmaterial, whose produced exterior skin product is a hybrid material,wherein the planking can also be molded and joined through furtherprocessing. The planking 5 will exhibit a fire-safe(r) behavior, and canalso be molded to reflect the outer contour of the exterior skin 2. Itmay be realized with a GLARE material. Otherwise, the preventative firesafety could already be implemented by joining the exterior skin 2 withplanking 5 tailored to its outer contour, with the entire outer surfaceof the exterior skin 2 being coated, of course. Given this assumption,the exterior skin 2 can even be realized with a material comprised of analuminum or aluminum alloy, joined precisely to the bum-throughresistant, plate-like planking.

It is believed that an aircraft fuselage made burn-through resistant isused to achieve the highest level of safety for a passenger planerelative to fire exposure from outside. A bum-through resistant aircraftfuselage may afford optimal protection against fire entering the cabin,since it is the furthest removed from the passenger seat installedwithin the fuselage, and prevents flames from penetrating at theirsource. If the aircraft fuselage is now manufactured out of burn-throughresistant materials, e.g., as possible with carbon fiber structures, itmay also become unnecessary to assemble burn-through resistantattachment elements for mounting an additional “fire barrier” (notdiscussed in any greater detail here), which is enveloped by a fuselageinsulation situated in the space 4 and completely encapsulated by aburn-through resistant film made of a fireproof film material. Theso-called fire barrier should function should be defined as a minimalrequirement for the fuselage structure, since this requires noweight-increasing, additional components to ensure burn-through safety,although the latter will likely not be as high as would be the case withthe introduced aircraft fuselage.

Advanced, truly reliably burn-through resistant aircraft can also berealized by having the exterior skin 2, which most often normallyconsists of an approx. 1.5 to 3 mm thick aluminum sheet, be replacedwith burn-through resistant sheets of the kind introduced.

Burn-through resistant exterior skin sheets can be realized using thefollowing materials, for example:

-   a) Carbon fiber materials (CFK) consisting of aramide,-   b) Glass fiber materials (GFK),-   c) Fireproof metals like titanium,-   d) Ceramic fiber materials, and-   e) Silicate fiber materials.

The advantage to these materials is that they exhibit a clearly highermelting point than is the case for aluminum.

As a result, these materials are distinctly more resistant in cases offire.

The different materials can be combined with each other to achieveoptimal properties with respect to processing, strength, weight andbum-through behavior. Reference is then made to so-called “compositematerials” or “sandwich structures”. In this case, the differentmaterials are adhesively bonded or glued to each other. A behavior infires may be further optimized or improved by using especiallytemperature-resistant adhesives here.

The burn-through resistant sheets fabricated in this manner can then beriveted with the ribs 6, 7 and stringer 8, just as conventional aluminumexterior skin sheets of the aircraft.

The reinforcing elements, called the stringer 8 and ribs 6, 7,responsible for the special structural integrity of the aircraftfuselage can also be made out of conventional materials (aluminum),since they are already inwardly situated relative to the exterior skin 2of the aircraft, and protected by the burn-through resistant planking 5against flames from a so-called “post-crash fire”. Even so, it ispossible to manufacture all other components, such as the stringer 8,ribs 6, 7 and clips, out of the same burn-through resistant material.

The following advantages to the proposed solution are believed to beachieved. In comparison to all other arrangements of a fire barrier fora passenger plane, the use of a burn-through resistant aircraft fuselageis particularly effective. No additional components are believed to benecessary, which is especially cost-effective and weight-neutral. Inthis case, the passenger may be protected against the propagation offlames into the cabin in comparison to all other similar solutions.Since the actual fuselage structure of the aircraft is protected againstburn-through, components traditionally mounted to the aircraft airframe,e.g., the interior cladding 3 and fuselage insulation, are preventedfrom falling on the passengers, endangering them or impeding theevacuation.

Reference List

-   1 Aircraft passenger cabin-   2 Exterior skin (of aircraft fuselage)-   3 Interior cladding-   4 Space-   5 Planking-   6, 7 Rib-   8 Stringer

1-16. (canceled)
 17. An aircraft fuselage, having a fuselage structure,comprising: an exterior skin which is designed to be part of thestructural elements that are components of the mechanical strengthbracing of the fuselage and help absorb its forces and is made ofmaterials designed to be resistant to shear, and incorporated as abearing element into the mechanical strength bracing to absorb andtransfer the forces and torques acting thereupon, wherein the exteriorskin is realized by a semi-finished material combining a non-metallicmaterial and a metallic material, such that the exterior skin is ahybrid material capable of being molded and joined by furtherprocessing, wherein the exterior skin comprises a non-metallic materialhaving fibers selected from the group of fibers consisting of carbonfibers, glass fibers, ceramic fibers, and combinations thereof and ametal material selected from the group of metal materials consisting ofan aluminum, a titanium, an aluminum alloy, a titanium alloy, andcombinations thereof, wherein the nonmetallic material and the metalmaterial are coated by a resin layer or imbedded in a resin.
 18. Theaircraft fuselage of claim 17, wherein the exterior skin includes asandwich design, adhesively bonding a composite material and the metalmaterial in layers, such that the sandwich design yields a burn-throughresistant exterior skin during exposure to flames from a fire.
 19. Theaircraft fuselage of claim 18, wherein the composite material is anon-metallic material having fibers selected from the group of fibersconsisting of carbon fibers, glass fibers, ceramic fibers, silicatefibers and combinations thereof.
 20. The aircraft fuselage of claim 19,wherein a material combination comprised of the various non-metallicmaterials is taken into account when manufacturing the exterior skin.21. The aircraft fuselage of claim 17, wherein the non-metallic materialincludes plastics reinforced with glass or plastic fibers.
 22. Theaircraft fuselage of claim 17, wherein the metal material is made oftitanium or of a titanium alloy.
 23. The aircraft fuselage of claim 18,wherein the composite material is of a GFK or CFK material and the metalmaterial is of an aluminum, an aluminum alloy, a titanium, a titaniumalloy, or combinations thereof.
 24. The aircraft fuselage of claim 18,wherein the composite material is a heatproof composite material,exhibiting a temperature resistance and tensile strength when exposed tohigh temperatures during a.
 25. The aircraft fuselage of claim 24,wherein the heatproof composite material includes carbon fibers coatedwith material from a nitride or carbide bond, and a metal or ceramicmaterial, into which the coated carbon fibers are imbedded.
 26. Theaircraft fuselage of claim 18, wherein the sandwich design is realizedusing a glare material, having a high burn-through behavior.
 27. Theaircraft fuselage of claim 17, wherein an outer surface of the exteriorskin exposed to weathering is joined with a plate-like planking theplanking being comprised of a non-metallic material, a fireproofmetallic material, or a combination material, the combination materialbeing comprised of a non-metallic material and a metal material, suchthat the planking is capable of being molded and joined by furtherprocessing.
 28. The aircraft fuselage of claim 27, wherein the plankingis formed such that the planking is protective against burn through andadjusted to an outer contour of the exterior skin.
 29. The aircraftfuselage of claim 28, wherein the planking is realized using a glarematerial.
 30. The aircraft fuselage of claim 29, wherein the exteriorskin comprises(2) an aluminum or an aluminum alloy joined to theplanking.